How to reverse rotation and speed control Universal motor ?

Thread Starter

pap25

Joined Oct 26, 2010
3
Please Help..I've to use universal motor to drive a pulley and belt .

The operation is the belt can move both way(forward and backward),
So the motor have to rotate in both direction too.
{operation like a picture but use motor instead}


I know that reverse current direction doesn't reverse rotation.
Could you tell me how can I do to reverse direction of this motor (not permanent)

motor spec


sewing motor (OLYMSIA)
POLES 2 VOLTS 220 V INPUT 120 W
OUTPUT 63 W AMP'S 0.6 A
A.C. 50/60 HZ
Input 2 lines AC 1 Phase
 

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Last edited:

bertus

Joined Apr 5, 2008
21,364
Hello,

As far as I know this type of motor can not be reversed.
In a sewing machine a gearbox does the reversel.

Bertus
 

johnno08

Joined Oct 26, 2010
2
have you tried to reverse the stator polaraty against the armature windings ?

this is how the motor is reversed in a washing machine

just a thought
 

Kermit2

Joined Feb 5, 2010
4,162
The brushes in a universal motor are tied to the same lines as the stators, so the rotor switches polarity the same as the stator poles. To reverse it you must 'CUT' the two lines to the stator/rotor and put a double pole double throw switch in.

You want to cross the connections to the rotor brushes, but not the lines to the stator. Hook the cut lines from the stator to the two end poles of the switch and put the rotor/brush wires the center poles of the switch. attach two jumpers to the other end of the switch and 'cross' them and attach to the first end.

 

eblc1388

Joined Nov 28, 2008
1,542
Theoretically one can reverse the rotation of an universal motor but in reality there are pitfalls.

The brushes in an universal motor are usually skewed from the neutral axis to counter the effect of what is known as "armature reaction". Correctly placed the sparking at the armature commutator is barely visible.

I once fitted a toggle switch switch to reverse the rotation of an electric drill motor but resulted in horrible sparking at the armature to the extend that I have to cancel the whole idea.
 

thatoneguy

Joined Feb 19, 2009
6,359
They cannot be reversed. They are designed to turn in one direction, if either AC or DC is used. The brushes are not adjustable for "phase" (as mentioned in the post above) to allow anything near efficient operation even if the actual field is reversed.

Suggest a DC motor w/H-bridge for project.
 

R!f@@

Joined Apr 2, 2009
9,747
I have something similar in mind.. see the pic



I too am trying reverse this drill.
Do u think this is a bad idea... ?
All I have to do is reverse the brush connection, right?

The Hi Lo switches bypasses the diodes for dual speed
 

thatoneguy

Joined Feb 19, 2009
6,359
I have something similar in mind.. see the pic



I too am trying reverse this drill.
Do u think this is a bad idea... ?
All I have to do is reverse the brush connection, right?

The Hi Lo switches bypasses the diodes for dual speed

It looks like the Hi/Lo switch simply feeds half wave to the motor rather than full wave. It doesn't appear to be full variable speed.

Are there permanent magnets in the drill, is there a field winding?

If you do reverse the brushes, and get a LOT more sparks at the brushes, it was designed to rotate in one direction only. The brushes "lead" the coils for more torque in the designed direction.
 

debe

Joined Sep 21, 2010
1,237
Some pics of a common variable speed & reversable AC/DC electric drill & a diagram. Also when these motors are run in reverse there is more arcing on the comutator, but i guess the manufacturer asumes they wont be run in reverse for long periods. Hope this is of some help. Daryl
 

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R!f@@

Joined Apr 2, 2009
9,747
I do not need to vary the speed.. The customer wants to have it reversible. tht's all

@debe
I once fix the switch of that same type.

From the looks of it, they are the same type of universal motors. Am I right?

So reversing isn't a problem...or is it?
 

debe

Joined Sep 21, 2010
1,237
Hi R!f@@, I suspect most electric drills are basicly the same construction. Yes they are reversable as the one in the pic is the rev switch is the lever on top of the speed control. Inoticed that the drill does arc on the comutator more in reverse than foreward. These drills are very cheep here in Australia about $39. Daryl
 

R!f@@

Joined Apr 2, 2009
9,747
The thing is I never tried this before. But I have seen the same motor's used in reversible ones. So what's the big deal in bit of arcing.

I just like to know tht by simply reversing the brush, the motor will reverse or not.
The diagram is some what confusing

OH! the rotor has to be reversed to reverse the motor..
so what will happen if reverse 1 field?
 

debe

Joined Sep 21, 2010
1,237
You need toReverse both fields in the diagram the current is fed through both fields to the brushes. The switch is a 2 position 3 pole switch, the center poles are fed from the 2 fields. the grey wires from brushes go to one end of the switch. These conections are briged to oposite sides at th other end of the switch. This way the brush conections are being swaped to each field for reversing. If you have trouble will post a pic of how the switch is wired? Daryl
 

debe

Joined Sep 21, 2010
1,237
Posted a representative pic of how the switch should be wired. However since the electric drill in your pic is a DOUBLE INSULATED device you shouldnt use a metallic switch. Is it realy worth doing??
 

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R!f@@

Joined Apr 2, 2009
9,747
hey if customer wants it, who am to argue.

It's A DPDT switch. Same as H-bridge reversal method. nothing fancy

I will try it.
Post back later
 

R!f@@

Joined Apr 2, 2009
9,747
After Going through all the details, I decided to do this.
I could not find the correct size switch for the job, so I went for the alternative.
It wasn't easy to cut the brush connection and to add and extend the required connections. It was a tight fit though.

Could not take out the field, so I have to rely on experience to cut the points



After that extended the necessary wires.





I discarded the H/L speed rectify and used it's switch to toggle a relay instead.
Connections were made as per Kermit's diagram.
The Relay power is derived simply via diode, a cap and drop out resistor.



All in all, not a bad job. Drill Reverses perfectly. but as said before the reverse mode does produces a lot of spark.

So , not to operate in long duration in reverse mode was advised to the customer.
 
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